Development of immunity to Ostertagia ostertagi (Trichostrongylidae: Nematoda) in pastured young cattle.

This experiment comprised 3 groups of calves, (+P2), (-P2) and (-P1), which all started their first grazing season as parasite-free calves. The (+P2)- and (-P2)-group grazed 2 seasons. In the first season the (-P2)-group of calves was grazing a pasture with no detectable trichostrongyles and treated with anthelmintics every second week. The untreated (+P2)-group grazed an Ostertagia ostertagi contaminated pasture. During the second grazing season these 2 original groups grazed together with a new group of first-year grazing calves (-P1) on paddocks infected with O. ostertagi. Parasitological analyses showed that (+P2)-group had negligible egg excretions in the second year in comparison with (-P2) and (-P1). This indicated, that the egg output may be regulated through acquired immunity. The difference in egg excretions was not reflected in the serum pepsinogen levels, which were only slightly elevated for all groups in the second year. Post mortem examination at the end of the experiment showed that only the (-P1)-group harboured relatively high numbers of worms in the abomasa at that time. Antibodies of 3 immunoglobulin classes were investigated: IgA, IgG1 and IgG2. The IgA and IgG1 responses correlated with the presence of developing and adult worms in the abomasa and they remained elevated in the (+P2)-group throughout the experiment, perhaps indicating an involvement of these antibodies in a protective immune response. In the (-P2)-group the IgA and IgG1 showed fast and sharp rises during the second season that most likely were age-related and as such a result of maturation of the immune system. The role of IgG2 is unclear as the IgG2 response was weak in all groups of calves and difficult to relate to the parasitological data.

Preventive anthelmintic treatment of grazing young cattle via supplementary feed and drinking water.

Twenty-six first season calves were allocated into four groups which were turned out on May 21 to graze separate permanent pastures. One group (group A) remained untreated. The others were treated each month with albendazole either as an oral drench (group B) through supplementary feed (group C) or through the drinking water (group D). Neither clinical disease nor weight gain depressions were observed in any group. Although the infection levels were low, the faecal excretion of trichostrongylus eggs, the serum pepsinogen activities and the pasture larval contamination all indicated a marked reduction in the levels of infection of groups B, C and D. The serum pepsinogen activities of groups B and C were similar and remained below 1 unit of tyrosine/litre of serum whereas that of group D was intermediate between these two groups and group A. The labour saving principle which was applied to group C is recommended under conditions similar to those of the present experiment.

[Fascioliasis in sheep in South-western Jutland (author's transl)]. / Fascioliasis hos får i Sydvestjylland.

The frequency of fascioliasis in sheep of south-western Jutland has been determined on the basis of slaughterhouse registration of infected livers over a 5-year period (1969-1973). The average yearly percentage of adult sheep found to be infected ranged from 83.9 to 91.2%, whereas less than 1 % of the slaughtered lambs proved infected. The high infection percentage among adult animals and the strikingly low frequency among slaughter lambs could be explained by the characteristic management system of the marshland: In summer the sheep graze the dike and the foreland on its seaward side, and in winter the animals graze in the marshland. Lymnaea truncatula is not found on or at the seaward side of the dike, whereas it is abundant all over the marshland. Thus the lambs graze exclusively the snail-free area from which they are taken directly to the slaughterhouse. The summer grazing also protects the adult animals as they avoid the massive uptake of metacercariae which normally takes place in fluke infected areas in late summer.